1. Technical Field
The present disclosure relates to a wireless power-transmission system having a function for detecting a foreign substance (also referred to as “a foreign object”) between coils and to a power transmission apparatus in the wireless power-transmission system.
2. Description of the Related Art
In recent years, electronic equipment and electric vehicle (EV) equipment, such as mobile phones and electric vehicles, that involve movement have come into widespread use. Wireless power-transmission systems for such equipment are being developed. In the wireless power transmission technology, an electromagnetic induction scheme, a magnetic-field resonance scheme (a resonance magnetic-field coupling scheme), an electric-field coupling scheme, and so on are known.
Wireless power-transmission systems based on an electromagnetic induction scheme and a magnetic-field resonance scheme include a power transmission apparatus having a power-transmitting coil and a power receiving apparatus having a power-receiving coil. A magnetic field generated by the power-transmitting coil is complemented by the power-receiving coil, so that power can be transmitted without direct contact of an electrode. One example of such wireless power-transmission systems is disclosed in Japanese Unexamined Patent Application Publication No. 2009-11129 (Patent Document 1).
In such related art, however, there are demands for a power transmission apparatus that performs highly efficient power transmission.